I've sorted my idle speed problem out !!!!!!!!!! Bad news and good news. Bad news was that it required a new idle speed ecu. Are these a common failure? Seeing as though I needed a new one I decided to take the old one out and have a look inside (I did electronic engineering for my degree and I don't get out much ! ) The case is definately NOT designed to come apart easy so I had to cut it open. I did this underneath so if glued back together it would appear original when screwed back in place behind the drivers seat. I looked at the components inside and couldn't believe how basic it is, well, compared to new ones anyway. Good news, after some quick checks on the transistors and looking for dry joints on the circuit board I decided to see if you could still get the IC's (chips). I recognised 3 out of the 5 straightaway (I said I don't get out much) and with some quick cross matching with the others I made a list. I also decided to get plug in sockets for the chips so I could change them quick in the future (no jokes here please about being made in Japan or substituting them for 1950's valves). Guess how much? Approx £3.50 for the lot from Farnells. The question is, did it work? Answer YES IT DOES. I am now a happy bunny with a lovely running engine, well, apart from the rich mixture at startup. I think I'll strip down the warm-up regulator at the weekend for a look. I managed to borrow a digital pressure indicator from work so I will test all my fuelly bits this weekend (assuming I don't get called out) Wish me luck! btw, I bought enough chips to do 2 ecu's. If anyone wants me to have a go at repairing thiers then let me know. If this is a common failure then I may have some work on with the club ! If anyone wishes to do the same, i have supplied an excel spreadsheet with the order codes and prices from Farnells. Please note that a minimum order is probably required, I bought a new soldering iron at the same time.
Nick.
"nickandkathryntomlinson <nickandkathryntomlinson@xxxx>" <nickandkathryntomlinson@xxxx> wrote:
To All Delorean Tech-heads.
Please excuse me if you have heard of this problem before but I am
fairly new to the world of Delorean ownership.
I have a problem with the idle speed on my car (Automatic) when the
engine is cold. It also appears to run rich although this maybe
associated with this problem.
I have just tuned the engine and have performed the following
changes/ tests.
Changed spark plugs (plug gaps set to 0.68-0.70mm)
Checked throttle is fully closed (including checking the throttle rod)
Checked microswitch engages correctly and is electrically OK.
Checked Distributor timing and vacuum advance shut off solenoid.
Checked Fuel Canister purge valve/ isolated carbon canister (removed
and plugged hoses)
Changed Lambda/O2 sensor
Checked Frequency valve `buzzez'
Checked Supply voltage and earth return at Fuel Control Pressure
Regulator.
Checked for 35 ohm resistance for Fuel Control Pressure Regulator
heater.
Adjusted Fuel Distributor flap so frequency valve duty cycle
oscillates between 32 and 45 on a dwell meter. (Note I have re-
plugged the adjustment hole when taken a reading).
Check Idle Speed control valve for operation.
Pins 1 and 2 approx 100 ohms
Pins 2 and 3 approx 100 ohms
Pins 1 and 3 approx 200 ohms
With +12v on Pin 2, momentarily earthing Pins 1 and 3 in succession
successfully opens and closes the control valve.
Checked continuity of cabling from the control valve back to the
plugs on the idle speed ecu.
Checked thermistor resistance at idle speed ecu. Reads approx 1.8-2
Kohms with engine cold, approx 220-290 ohms engine warm.
When the engine is warm the engine idles pretty smooth, varies +/- 50
RPM at approx.780 RPM.
The engine speed does drop when the air conditioning/ heated rear
window and lights are put on.
As a further test I have at the ecu end put a manual variable
potentiometer (resistor) that can vary the resistance between 0 and
5k on the ecu to simulate the idle speed thermistor. I used short
cables to connect the other connectors to the ecu using standard
spade/ blade male female connectors.
I presumed that changing this resistance would make the engine idle
speed raise and lower as it would change the duty cycle oscillations
on the idle speed valve but this has no effect.
Am I right in thinking that my idle speed ecu is at fault?
I've check the other connectors i.e. supply voltage, earth, idle
switch operation, connection back to coil, continuity to idle speed
valve, protection diodes etc.
My other test tonight when the engine is cold would be to use a
standard auxiliary air valve used on standard volvos to simulate the
extra air required for a cold engine. OK, I don't have the correct
valve so I've improvised (don't laugh) by using a 22mm plumbing
isolator valve in place of the idle speed valve (in effect a gate
valve). I tried this out on a warm engine and it raises/ lowers the
idle speed ok. (Can't imagine screwing this slowly down while in
traffic !!)
Can anyone advice anything else I can try before I buy a replacement
idle speed ecu?
Can anyone let me know what the idle speed of their Delorean is at
cold and how long roughly it is high for? My car is an automatic.
When warm the engine drives really smooth and is a joy to drive, when
cold I have to use my left foot on the brake.
Thanks all in advance for any further help
Nick Tomlinson ? DOC Member 241.
p.s. If anyone has a "spare" ECU I could try then i'd be v. grateful.
If this is a common problem I could try and source and test a few
from a breakers yard. Apparrently the same ECU could come from a
Volvo 200 and 700 series with the PRV engine.
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